This study examines urinary TGF-B excretion as a non-invasive molecular marker of disease activity in children with nephrotic syndrome. The study involves a measure of renal function (serum creatinine) and urinary TGF-B excretion at baseline and again 12 months later. In addition, Angiotensin Converting Enzyme (ACE) gene polymorphisms are measured because TGF-B expression is increased by Angiotensin II and the ACE polymorphisms have been associated with disease progression in other sclerosing renal diseases. Separate analyses will be conducted to determine if the markers of disease severity and progression of disease correlate with urinary TGF-B activity and with ACE polymorphism gene frequencies, adjusting for ACE inhibition therapy.